A hydrocarbon resource may be particularly valuable as a fuel, for example, gasoline. One particular hydrocarbon resource, bitumen, may be used as a basis for making synthetic crude oil (upgrading), which may then be refined into gasoline. Accordingly, bitumen, for example, may be relatively valuable. More particularly, to produce 350,000 barrels a day of bitumen based synthetic crude oil would equate to about 1 billion dollars a year in bitumen. Moreover, about 8% of U.S. transportation fuels, e.g., gasoline, diesel fuel, and jet fuel, are synthesized or based upon synthetic crude oil.
In the hydrocarbon upgrading or cracking process, hydrogen is added to carbon to make gasoline, so, in the case of bitumen, natural gas is added to the bitumen. Natural gas provides the hydrogen. Bitumen provides the carbon. Certain ratios and mixes of carbon and hydrogen are gasoline, about 8 carbons to 18 hydrogens, e.g. CH3(CH2)6CH3. Gasoline is worth more than either bitumen or natural gas, and thus the reason for its synthesis.
Synthetic fuel is manufactured in upgraders and refineries at the surface, after the bitumen resource is extracted from the earth. Bitumen is usually strip mined or extracted by wells using enhanced oil recovery technologies (EOR), such as, steam assist gravity drainage (SAGD). Strip mining may be undesirable for environmental reasons and typically only those deposits near the surface are economic. SAGD may be undesirable because of its relatively slow speed, unreliable startup, payzone caprock integrity to include the steam, steam loss due to thief zones and wormholes, and stranded pay zones due to impermeable layers. Enhanced oil recovery by radio frequency well heating may be impacted less from these limitations and may be three or more times faster for increased value and profit. Unlike conducted heating, RF heating energy may instantaneously penetrate many feet.
Hydrocarbon reservoirs often include water. A hydrocarbon rich oil sand, from the Athabasca Province of Canada is, for example, a porous microstructure having sand grains in a water pore, surrounded by a bitumen fill. Analysis by the Alberta Research Council indicates the weight proportions of rich sand is between 14-16 percent bitumen, 0.5 to 2.0 percent water, and the remainder sand and clay. A lean oil sand may include 5 to 10 percent bitumen (or less of course), and 6 to 9 percent water. Hydroxyl radicals are typically present in the water, and salts and dissolved carbon dioxide may present, so the connate waters and ores have a range of electrically conductivity. Dissolved carbon dioxide may form a weak solution of carbonic acid, which is a conductive electrolyte. At 1 MHz radio frequency, the electrical conductivity of the rich oil sand may be 0.002 mhos/meter, and a lean oil sand 0.2 mhos per meter, so reduced hydrocarbon content may mean increased moisture and increased electrical conductivity. The electrical nature of oil sand also changes as the material is heated.
Several references disclose application of RF to a hydrocarbon resource to heat the hydrocarbon resource, for example, for cracking. In particular, U.S. Patent Application Publication No. 2010/0219107 to Parsche, which is assigned to the assignee of the present application, discloses a method of heating a petroleum ore by applying RF energy to a mixture of petroleum ore and susceptor particles. U.S. Patent Application Publication Nos. 2010/0218940, 2010/0219108, 2010/0219184, 2010/0223011, 2010/0219182, all to Parsche, and all of which are assigned to the assignee of the present application disclose related apparatuses for heating a hydrocarbon resource by RF energy. U.S. Patent Application Publication No. 2010/0219105 to White et al. discloses a device for RF heating to reduce use of supplemental water added in the recovery of unconventional oil, for example, bitumen.
Several references disclose applying RF energy at a particular frequency to crack the hydrocarbon resource. U.S. Pat. No. 7,288,690 to Bellet et al. discloses induction heating at frequencies in the range of 3-30 MHz. More particularly, radio frequency magnetic fields are applied to ferrous piping that includes hydrocarbons. The magnetic fields induction heat the ferrous piping and the hydrocarbons inside are warmed conductively. Application Publication No. 2009/0283257 to Becker discloses treating an oil well at a frequency range of 1-900 MHz and no more than 1000 Watts, using a dipole antenna, for example.
U.S. Pat. No. 7,115,847 to Kinzer discloses a method of capacitive RF heating using impedance matching techniques to increase efficiency of hydrocarbon resource recovery. More particularly, Kinzer discloses setting a signal generating unit to an initial frequency and changing the frequency based upon a load impedance.
U.S. Pat. No. 4,819,723 to Whitfill et al. discloses a method of reducing the permeability of a rock formation to address the problem of fluid loss to highly porous subterranean formation. Whitfill et al. discloses pumping an emulsion including an alkali metal silicate, i.e. sodium silicate, into a well in the subterranean formation. A microwave generator is lowered into the well via a cable until it is adjacent a permeable zone. Microwave energy is applied into the permeable zone to cause the emulsion to break and release the sodium silicate. The released sodium silicate, upon contact with brine in the permeable zone, forms a plug of gel to block the remainder of the zone from the well.
Further improvements to hydrocarbon resource recovery, or heating or upgrading may be desirable. For example, it may be desirable to increase the efficiency of startup of an uninsulated well by making it quicker and cheaper, for example.